The present invention relates to a process for removing a multiple coating film, or an adhering substance and a layer of a cured adhesive agent, and a process for forming a multiple coating film.
Presently, recycling of resources is an important problem. In order to recycle resources efficiently, and to reuse the substrate (or base material) of a coated material, removal of the coating from the substrate is necessary. Also, in order to reuse a substrate to which a layer such as cloth or paper is adhered with an adhesive, removal of the adhering layer and the cured adhesive itself is necessary.
Several well-known processes have previously been used for removing a coating layer from a substrate. These include mechanical removal by impact, combustion, dissolving with organic solvent and scraping away a coating film swelled with a solvent. None of these has been entirely satisfactory. Mechanical removal by impact and combustion are often difficult to use with plastic substrates. Processes involving dissolution by an organic solvent and scraping away a coating film swelled with a solvent are limited in their applicability because of dissolution of the substrate with the solvent. It is especially difficult to remove a coating film containing a resin which has a high molecular weight and has a low crosslinking degree as a binder, since the coating film is apt to cling to the substrate. In the case of a coating film having a high degree of crosslinking, it is not always easy to remove the coating from the substrate.
A dried layer of an adhesive agent obtained from an emulsion of non-crosslinkable adhesive agent typically has poor water resistance. As a result, such adhesive agents exhibit poor adhesion when wetted with water. In addition, a cured layer of an adhesive agent obtained from a crosslinkable adhesive agent has good performance in both water resistance and adhesion, but otherwise it is difficult to remove an adhering substance such as cloth and paper and the cured layer of adhesive agent itself.